Using a stepper motor as a motion encoder

Philldapill

I was a little bored yesterday, so I decided to fiddle with some of my "toys". I was playing with a stepper, and decided to see what the output looks like on a scope. Once I got it hooked up, and gave it a small turn, my head started "spinning" with ideas. Has anyone ever used a small stepper as an input device? I'm thinking that I could use a few opamps to clean up the signal, and then let a micro(the Propeller) count the pulses from each winding. With a bit of logic, I think the propeller could easily keep track of the angular position of the stepper.

Anyone have any experience or "input" on this?

James Newman

I've seen it done on a few sites. I got the impression that you'd never want to use this for critical tracking, ala motor encoders... but that it'd work decent for input such as volume knobs or rotary selectors.

Don't have any links on me, but the first result on google for 'Stepper as encoder' is www.4qdtec.com/stpen.html

kwinn

Stepper motors can bd used as encoders but the signal is proportional to speed so you may need to amplify it for volume control or selector use. They can also be used as alternators to generate power.

virtuPIC

Looks similar to using brushless motors as generators. Well, brushless motors are also kinda steppers - but with only 3 or 6 steps per rotation.

Regarding the steppers, voltage and current depend on speed. If you turn fast enough you'll get clear signal and might even use it to power the prop. But you can't use it in a seismoscope. Movement is too small and too slow.

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Phil Pilgrim (PhiPi)

If the motor were hooked up as a generator, you'd risk losing pulses if the rotation speed were very slow. I'd be more inclined to energize the coils slightly with a constant voltage, thereby creating a sight detent. You may find that the coil current varies statically as the shaft rotates between detents.

-Phil